Category: RTL-SDR

Receiving up to 4.5 GHz with an RTL-SDR and a $5 Directv Downconverter

KD0CQ has recently been experimenting with trying to receive signals at frequencies of up to 4.5 GHz with an RTL-SDR and downconverter. Since a typical R820T/2 RTL-SDR’s maximum frequency limit is about 1.7 GHz, an external downconverter circuit is required. A downconverter converts high frequencies down into the range receivable by the RTL-SDR. For example a downconverter with a 2.4 GHz local oscillator would convert a 3.5 GHz signal down to 1.1 GHz, which can be easily received by an RTL-SDR.

The secret to doing this cheaply is revealed by KD0CQ. He shows that a very cheap $5 Directv SUP-2400 upconverter can be converted into a 2.4 GHz downconverter simply by removing some filters. He writes that he hasn’t uploaded the full set of steps to modify the SUP-2400 yet, but he intends to do so in the near future.

There is also a discussion about this mod on Reddit. Several posters have been discussing what applications a cheap downconverter could open up. Some mentioned applications include receiving various satellites in the C/S bands, DECT cordless phones @ 1.9 GHz, SiriusXM satellite radio @ 2.3 GHz, ISM @ 2.4 GHz, RADARs, RC aircraft control/telemetry/video and ham beacons.

The SUP-2400 Directv upconverter that can be converted into a downconverter.
The SUP-2400 Directv upconverter that can be modified into a downconverter.

$5 Microwave Downconverter for the RTLSDR KD0CQ

Hearing Ethernet Packets with an ESP8266 and RTL-SDR

Over on YouTube CNLohr has posted a video showing an interesting side effect of implementing ethernet on the ESP8266. The ESP8266 is a very popular $7 wifi module for microcontrollers that has found a lot of extra use outside of its intended design. Previously CNLohr also showed how Analogue NTSC TV could be broadcast with the ESP8266. Recently it was found that (software based) ethernet capability could be hacked into it.

In his new video CNLohr demonstrates that AM radio can be broadcast by attaching a short wire antenna to the ESP8266 ethernet output, and then using an RTL-SDR to receive one of its harmonics at 150 MHz. He shows that by varying the size and speed of the packets he can change the received tones, and even create notes to play music. This essentially gives a simple way to ‘hear’ ethernet. 

Broadcasting AM Radio with Ethernet on the ESP8266

A new RTL-SDR based Portable ADS-B Kit for Pilots is on Kickstarter

Back in March we posted about the FlightBox, a portable RTL-SDR ADS-B 1090ES and 978UAT receiver built for use by pilots in small aircraft. 1090ES provides ADS-B which allows a pilot to see on a map where other aircraft are, and 978UAT provides other services such as weather radar. The FlightBox is essentially a Raspberry Pi 2 combined with two RTL-SDR dongles, two antennas, a GPS receiver and is preloaded with the stratux software. The two channel FlightBox receiver currently sells for $250 USD.

Recently a new similar ADS-B product for pilots made by a different company has been released on Kickstarter. The new product is made by a company called RF-Connect and is similar to the FlightBox, but is powered by an Odroid C1. RF-Connect are also the programmers behind the ADS-B on Android app which was one of the first apps to be able to receive FIS-B weather data and display it on a map. 

The product receives 978UAT and 1090ES ADS-B signals using two RTL-SDR dongles, and then transmits the data via WiFi to an Android or iOS tablet running flight navigation software.

The Kickstarter early backer price is $150 USD for a single channel 978UAT only capable receiver or $200 USD for the dual channel 1090ES and 978UAT receiver. This contrasts with the FlightBox price of $200 and $250 USD for similar products, however the standard backer price for the RF-Connect ADS-B receiver is the same as the FlightBox.

The RF-Connect ADS-B Receiver transmitting data to a tablet.
The RF-Connect ADS-B Receiver transmitting data to a tablet.
The parts inside the ADS-B Receiver. Two RTL-SDR dongles, GPS receiver, two antennas, WiFi dongle, Odroid.
The parts inside the ADS-B Receiver. Two RTL-SDR dongles, GPS receiver, two antennas, WiFi dongle, Odroid.

RF-Connect have also uploaded a video showing their ADS-B on Android app in action.

OpenFest 2014: Software Defined Radio and RTL-SDR by Harald Welte

Recently some talks from the OpenFest 2014 conference have been uploaded to YouTube. One of the talks uploaded is titled “Software Defined Radio and RTL-SDR” and is by Harald Welte. Although a couple of years old, the talk is still valid and quite clearly explains some concepts about how software defined radio works, and then goes on to talk about the RTL-SDR dongle and some of it’s applications. The introduction reads:

This talk is about getting started with the basics of software defined radio (SDR). It introduces the fundamental concept of SDR constrasting classic radio systems, and continue to cover the rtl-sdr project, a software/driver architecture for the ultra-cheap RTL2832U based hardware. There will be practical demonstration using some of the readily-available Open Source projects implementing receivers for various radio systems.

If you are interested in his talk, then his slides appear to have been uploaded here.

Software Defined Radio and rtl-sdr - Harald Welte

Software De-Dispersion of RTL-SDR Pulsar Data

Back in September 2015 we posted about how radio astronomers Peter W East and GM Gancio were able to use an RTL-SDR dongle for the radio astronomy task of detecting pulsars. A pulsar is a rotating neutron star that emits a beam of electromagnetic radiation. If this beam points towards the earth, it can then be observed with a large dish antenna and a radio, like the RTL-SDR. 

More recently they published a new paper titled “Software De-Dispersion of RTL-SDR Pulsar Data” (pdf).  De-dispersion is a technique that allows very weak signals to be extracted from the background noise. The introduction to the paper reads:

Data files produced by RTL SDR dongles can be folded directly for pulsar detection using software such as rapulsar.exe. Using simple I/Q vector averaging software, the data can be down-sampled by factors of more than 100 prior to folding and/or period search processing to speed up useful data extraction. Ideally, wide band RF data should be de-dispersed to optimise later search and folding processing. De-dispersion is normally carried out by time adjusting data sampled from RF filter banks before combination. This note describes how data already digitised from the RTL SDR can be spectrum analysed or filtered using the FFT algorithm. Two methods are discussed, one summing power with some down-sampling; the second, a ‘coherent’ method that de-disperses the rtlsdr.exe .bin data file and outputs a .bin-compatible file. Both accurately de-disperses the data offering an improved folded data SNR.

More information about radio astronomy with the RTL-SDR, pulsars and the associated software links can be found at Peter W East’s webpage http://y1pwe.co.uk/RAProgs/index.html.

The de-dispersion principle
The de-dispersion principle

New Book out by the Author of the RTLSDR4Everyone Blog

Akos, the author of the rtlsdr4everyone blog has recently released a new Kindle book on Amazon which sells for $5 USD. It is titled “RTL-SDR for Everyone: Second Edition 2016 Guide including Raspberry Pi 2”. Akos writes that the book is intended for beginners and anyone wishing to maximise their RTL-SDR dongle’s performance. The blurb reads:

Chapters cover all you need to know for the best reception with $10 RTL-SDR dongles. Wideband and specialist antennas, modding and noise reduction tips aided with images and diagrams.

My blog at http://rtlsdr4everyone.blogspot.com is only a fraction of the know-how in this book – if you want to take performance to the next level, or simply have no time to waste searching for information on the Internet, then this book is for you.

Readable on all platforms: Windows and Mac, Android and iPad, iPhone and Ipod touch.

Chapter 1 begins with Akos explaining some of the theory and jargon used in the radio world. Chapter 2 of the book talks about the hardware such as the RTL-SDR dongles, coax cabling, connectors and preamplifiers. Chapter 3 talks about the software and includes installation guides for programs like SDRsharp, SDRConsole, Virtual Audio Cable, as well as tutorials for receiving signals such as weather satellites and ADS-B. Chapter 4 goes on to talk about the different types of antennas and Chapter 5 discusses how to maximise the performance of the RTL-SDR. Finally Chapter 6 discusses the Raspberry Pi and it’s links to the RTL-SDR.

A preview of the first few pages in the book is available on Amazon and remember that there is no risk with buying Kindle books as they can easily be fully refunded within the first seven days of purchase.

rtlsdr4everyone_book

Using an RTL-SDR to help Build Dynamic Spectrum Access Prototypes + DARPA Spectrum Collaboration Grand Challenge

Over on YouTube user Andre Puschmann has uploaded video showing his experiments with implementing dynamic spectrum access. Dynamic spectrum access is a upcoming technology that will allow the frequency spectrum to be more easily shared between many users. An IEEE paper describes Dynamic Spectrum Access in the following paragraph

Dynamic spectrum access is a new spectrum sharing paradigm that allows secondary users to access the abundant spectrum holes or white spaces in the licensed spectrum bands. DSA is a promising technology to alleviate the spectrum scarcity problem and increase spectrum utilization.

In his experiments Andre uses USRP and bladeRF software defined radios as the transmit radios, and an RTL-SDR as the receive radio. His video shows a video stream being received by the RTL-SDR which is not impacted by any spectrum frequency switches.

Building Dynamic Spectrum Access Prototypes using Open-Source SDR Software

In addition to this, DARPA has recently announced a new Grand Challenge that will focus on Spectrum Collaboration. We would expect SDR’s to be heavily used in this type of challenge. Their press release writes:

DARPA today announced the newest of its Grand Challenges, one designed to ensure that the exponentially growing number of military and civilian wireless devices will have full access to the increasingly crowded electromagnetic spectrum. The agency’s Spectrum Collaboration Challenge (SC2) will reward teams for developing smart systems that collaboratively, rather than competitively, adapt in real time to today’s fast-changing, congested spectrum environment—redefining the conventional spectrum management roles of humans and machines in order to maximize the flow of radio frequency (RF) signals. DARPA officials unveiled the new Challenge before some 8000 engineers and communications professionals gathered in Las Vegas at the International Wireless Communications Expo (IWCE).

The primary goal of SC2 is to imbue radios with advanced machine-learning capabilities so they can collectively develop strategies that optimize use of the wireless spectrum in ways not possible with today’s intrinsically inefficient approach of pre-allocating exclusive access to designated frequencies. The challenge is expected to both take advantage of recent significant progress in the fields of artificial intelligence and machine learning and also spur new developments in those research domains, with potential applications in other fields where collaborative decision-making is critical.

USA Frequency Allocations
USA Frequency Allocations

 

Videos Showing Rpidatv in action

A few days ago we posted about the release of Rpidatv, a program that allows a Rapberry Pi to transmit DATV without the need for any additional hardware. DATV stands for Digital Amateur TV, and can be received with an RTL-SDR using a program called leandvb.

Over on YouTube, the programmer of Rpidatv (Evariste F5OEO) has uploaded a video that shows a Rpidatv + leandvb system in action. The video demonstrates the touch screen GUI which can be used if a touch capable LCD screen is connected to the Raspberry Pi. It also shows the whole system in action with a video being transmitted from the Raspberry Pi camera to a Linux PC with an RTL-SDR running leandvb.

rpidatv with leandvb

Another video uploaded to YouTube by Qyonek also shows Rpidatv + leandvb in action.

Testy rpidatv + leandvb